Syrian rebel fighters carry their weapons as they walk near the front line in Retian village, north of Aleppo, Feb. 17, 2015. Photo: Reuters/Hosam Katan

ISTANBUL -- The Syrian civil war has a new flashpoint in the northern Aleppo countryside in the town of Retian, where both moderate and extremist rebel groups are fighting Assad regime forces, as well as the Islamic State group, in an under-the-radar battle. Over the past several months all factions have engaged in revenge kidnappings, keeping prisoners hostage and torturing them.

Although all these groups in Syria have been accused previously of kidnapping, torture and unlawful killings by international human rights organizations, they've recently stepped up their attacks in one particular, strategic location north of Aleppo. The combatants include forces linked to Hezbollah, the Shiite Lebanese militant group that is backing President Bashar Assad.

Retian lies on the road from Aleppo to Azaz, a town near the Turkish border. That route is still being contested. On another major transit route, the Islamic State group, also known as ISIS or ISIL, has dominated. It controls a road leading from Aleppo northeast to Al Bab, which is now one of the Sunni extremist group's major training centers.

This week several videos emerged on social media depicting different factions in Syria holding prisoners hostage. One video uploaded to Facebook Friday by rebels shows dozens of fighters lined up against the wall. Most of them had visible scares and bruises. Some of them were part of the Syrian military, while others were Hezbollah men fighting for Assad. The total number of regime-affiliated soldiers captured by rebel groups rose to 51 Friday, according to the Syrian Observatory for Human Rights.

In a separate but linked scenario, rebels fighting under the umbrella of the Free Syrian Army in the northern part of the country are kidnapping Shiite fighters from Afghanistan, who are being recruited by Iran to help Assad.

The Syrian Observatory confirmed in December that Assad has been using Afghan fighters on the ground in Syria for months. But now, the Afghans are being targeted by the rebels. Afghan fighters first started showing up in Syria in the fall of 2013. In May of last year, local media reported Iran's Revolutionary Guard Corps was recruiting Afghan Shiite refugees to fight in Syria and promising them $500 a month.

The Free Syrian Army has been kidnapping Assad soldiers and rebels from rival factions since the start of the war, but the kidnapping increased drastically in the summer of 2012 with the development of more extremist groups in Syria. The moderate rebels needed more money and weapons to keep up, so they turned to kidnapping for ransom.

The kidnapping by the rebels in the north could indicate they are once again in the same dire position they were in the summer of 2012 during the first battle for Aleppo. But it is still unclear what the various factions are gaining by kidnapping others and holding them hostage. None of the groups in the northern Aleppo countryside are conducting trades, or paying ransom.